UL 2353 is the Standard for Safety for insulated winding wire — and anyone can verify a supplier's UL file number for free. Here is the three-step method, using our own numbers as the example.
You receive a quotation from a winding wire supplier that says "UL certified" — how do you confirm it is real?This article explains what UL 2353 is, and a three-step verification method anyone can complete for free.We encourage you to verify every supplier — including us.
What Is UL 2353?
UL 2353 (Standard for Safety for Single- and Multi-Layer Insulated Winding Wire) is UL's formal safety standard for single- and multi-layer insulated winding wires (currently in its 3rd edition and recognized by ANSI as an American National Standard). It covers the material, electric strength, and thermal test requirements for products such as triple insulated wire. A manufacturer that passes evaluation receives a UL File Number (formatted like E236542), and its products appear in UL's official database, where anyone can look them up.
Note the hierarchy: UL 2353 is the standard; the E-file number is the evidence that a specific company has met that standard. When a supplier says "compliant with UL 2353," the key question is: "Please provide your UL File Number."
Three-Step Free Verification (No Registration Required)
- Step 1: open UL Product iQ
- Step 2: enter the file number the supplier provided into the search box (example: DAH JIN's E236542)
- Step 3: check the three elements of the result (the three points below)
- The company name matches the quotation (E236542 should show DAH JIN TECHNOLOGY CO LTD)
- The category code (example: OBJT2 = Single- and Multi-layer Insulated Winding Wire - Component)
- The listed model range covers the wire type you intend to purchase
A file number that cannot be found, a company name that does not match, or a category code unrelated to winding wire — each is a red flag your supplier needs to explain.
Bonus: Electrical Insulation Systems (EIS) Can Be Verified Too
Electrical insulation system: the system components of the electrical insulation systems (EIS, under the UL 1446 framework) used in transformers fall under a separate category, System Components, Electrical Insulation - Component (OBJS2). DAH JIN's DJ-130 insulation system is on file under E318181 (Class 130(B), with constituent components including TLW-BB and TLW-B7S), also searchable on Product iQ; customers adopting the DJ-130 insulation system require an Authorization Letter issued by DAH JIN.
Source: the standard title and current edition (3rd edition) of UL 2353 are as stated in the UL Standards Catalog (shopulstandards.com).
Frequently Asked Questions
I found the file number, but the model names differ from the quotation?
UL entries use the official model designations registered by the manufacturer. Ask the supplier to explain how the quoted models map to the UL-listed models — a legitimate manufacturer can answer immediately.
Can an SGS report count as certification?
SGS issues test reports (for example, RoHS testing per IEC 62321), which document specific test results for the submitted samples. This differs from certification schemes such as UL and VDE, which involve ongoing factory surveillance and authorized marks. Both have value, but they are not interchangeable. DAH JIN provides UL and VDE certifications plus SGS RoHS test reports, with the UL verification links published on our Certifications page.
Why are you willing to teach customers how to verify?
Because verification only benefits compliant manufacturers. Our file number and system number are printed on our website and documents — feel free to look them up right now.